Detailed stability analysis of reconstructed JT-60U equilibria indicates that the observed edge instabilities in JT-60U are consistent with the working model developed for DIII-D of ELMs as low to intermediate toroidal mode number kink/ballooning modes. The observed reduction in ELM amplitudes (giant to “grassy”) when the safety factor is increased by raising the toroidal magnetic field is likely due to the shift in the unstable modes to a higher toroidal mode number.

Transport studies with the GLF23 model for the ARIES-AT advanced tokamak reactor design indicate that 50MW of 120Kev neutral beam injection would not be sufficient to induce the toroidal rotation required to stabilize resistive wall modes. The transport modeling also leads to the surprising result that ExB velocity shear plays little role in the predicted better than H mode transport. In the high beta poloidal regime used for the design point of ARIES-AT, the Shafranov shift and negative magnetic shear are predicted to be the dominant cause of the reduced thermal transport.